Este trabalho trata da caracterização de propriedades termodinâmicas e de transporte de nanofluidos baseados em nanopartículas de alumina em água para diferentes concentrações. Suspensões estáveis foram elaboradas por meio de um agitador ultrassônico. As seguintes propriedades foram analisadas: i) condutividade térmica com o método da sonda-linear; ii) viscosidade dinâmica através do reômetro do tipo cone e placa e iii) ângulo de contato com base em registros fotográficos de gotas em uma superfície plana e o tratamento de imagem através de um programa elaborado em LabVIEW. Procedimentos foram utilizados visando validar os métodos experimentais adotados, entre eles a comparação com resultados para fluidos puros. Além do estudo experimental, foi realizada uma análise crítica da literatura sobre condutividade térmica e viscosidade dinâmica de nanofluidos. Com base nesta análise, os resultados experimentais foram comparados a dados empíricos da literatura e métodos de previsão de propriedades desenvolvidos para nanofluidos e para suspensões de particulado sólido em líquido. De uma maneira geral, os resultados levantados neste estudo para condutividade térmica e viscosidade dinâmica de nanofluidos foram significativamente superiores a maioria dos dados experimentais da literatura e aos resultados proporcionados pelos métodos de previsão. Entretanto, para nanofluidos com composições distintas de nanopartículas de alumina em água, comportamentos similares ao do presente estudo também são observados na literatura. No caso do ângulo de contato, verificou-se seu decréscimo com o incremento da concentração de nanopartículas. Tal resultado coincide com a bibliografia consultada, segundo a qual a molhabilidade do nanofluido se eleva com o incremento da concentração de nanopartículas. / The present study concerns the characterization of thermodynamic and transport properties of nanofluids based on alumina nanoparticles in deionized water. Stable suspensions were obtained using an ultrasonic homogenizer (Sonicator). The following properties were measured: i) thermal conductivity using the linear probe method, ii) dynamic viscosity through a cone-plate rheometer iii) contact angle, based on photographic of nanofluid drops on a flat surface and image processing through a program based on LabVIEW. The methods and experimental procedures were validated by performing measurements properties of pure fluids with well known characteristics. Besides the experimental study, it was performed a comprehensive literature review on thermal conductivity and dynamic viscosity of nanofluids. Experimental results were compared against the data from the literature and the respective predictive methods developed for suspensions of nanofluids and micro solid particles in liquid. Generally speaking, the nanofluid thermal conductivity and dynamic viscosity measured in the present study were higher than the empirical values from the literature and the values given by predictive methods. However, it should be highlighted that although for different compositions of nanofluids behaviors similar to the one observed in this study are also reported in the literature. In case of contact angle, it was found that its value decreases with increasing the nanoparticle volumetric concentration. Such results is coincident with literature reports according to which the nanofluid wettability, given in terms of the contact angle, increases with increasing the nanoparticle concentration.

A proposta busca reduzir a absorção de água dos agregados reciclados de Resíduos de Construção e Demolição (RCD), através do tratamento de sua superfície com hidrofugante, de maneira que estes não aumentem o consumo de água tampouco reduzam a resistência mecânica. Os agregados reciclados de RCD foram caracterizados quanto à granulometria, morfologia, porosidade, ângulo de contato aparente, absorção de água, análise de imagem e rugosidade superficial. Em seguida, os mesmos foram tratados superficialmente com dois tipos de hidrofugante: solução de silano e parafina. Todos os tratamentos permitiram reduzir a absorção de água dos agregados reciclados de RCD. O tratamento por imersão foi aquele que permitiu obter os melhores resultados e a menor variabilidade entre as técnicas. Os tratamentos hidrofugam a superfície, apesar da parafina apresentar maior molhabilidade. O tratamento com parafina apresentou, em termos de absorção de água, resultados inferiores e menos variáveis que o silano. Os parâmetros de rugosidade constataram que, ambos os materiais perdem seu perfil topográfico original quando tratados com parafina. Os diferentes agregados reciclados com cada hidrofugante foram aplicados em materiais cimentícios analisados no estado fresco e no estado endurecido. Os tratamentos reduziram a absorção e o consumo de água de mistura, porém afetaram negativamente as propriedades mecânicas, devido nova interface gerada (no caso específica de parafina) e falta de molhabilidade nas superfícies. / The proposal aims to reduce the water absorption of the Construction and Demolition Waste (CDW) recycled aggregates through hydrophobic surface treatment, so that these do not increase the concretes water consumption (nor reduce de mechanical strength). The CDW recycled aggregates were characterized regarding granulometry, morphology, porosity, apparent contact angle, water absorption, image analysis and surface roughness. Then they had their surface treated with two types of water-repellent: silane solution and paraffin. All treatments have reduced water absorption of the CDW recycled aggregate. Immersion treatment was the one that allowed the best results and the lowest variability between techniques. The treatments repel water on surface, despite the paraffin presenting better wettability. Paraffin treatment showed, in terms of water absorption, lower and less variable results than silane did. Roughness parameters found that both materials lose their topographic profile when treating with paraffin. The different recycled aggregates with each repellent were applied in cementitious materials analyzed in fresh and hardened state. The treatments reduced absorption and mixing consumption of water in the mixing, but adversely affect mechanical properties due to the new interface created (paraffin wax in special) and the lack of wettability on surfaces.

O presente estudo teve por objetivo avaliar a qualidade de painéis de partículas de média densidade (MDP), manufaturados a partir de bagaço de cana-de-açúcar e bambu (Dendrocalamus asper). A massa específica nominal foi 0,65 g.cm-3 e utilizou-se adesivo à base de uréia-formaldeído. O delineamento consistiu em 16 tratamentos, divididos em quatro Experimentos. Foram avaliadas as propriedades físicas (Massa Específica Aparente - MEA, Absorção de Água - AA, Inchamento em Espessura - IE e Taxa de Não-Retorno em Espessura - TNRE), mecânicas (Flexão Estática - MoR e MoE, Arrancamento de Parafuso de Superficie e Topo - APS e APT e Ligação Interna - LI, além do Perfil de Densidade, Molhabilidade e Resistência Natural. Os objetivos foram: I - Avaliar painéis de partículas de bagaço de cana com duas granulometrias (0,50 mm e 0,85 mm), tratadas e não tratadas em água quente; II - Avaliar os painéis adotando as mesmas variáveis do experimento anterior, porém, empregando partículas de bambu; III - Avaliar os painéis gerados a partir da mistura de ambos materiais nas proporções de 100%, 75%, 50%, 25% e 0%; IV - Avaliar os painéis constituídos com partículas termorretificadas de bagaço e bambu encoladas com três teores de adesivo (10, 12 e 14%). Os resultados do Experimento I mostraram que propriedades físicas (IE2h, IE24h, AA24h e TNRE), mecânicas (MoR, MoE, APS, APT e LI) e molhabilidade não foram influenciadas pelos fatores (granulometria e condição de partículas). Os fatores influenciaram de forma interativa o perfil de densidade de massa específica aparente da camada externa. A resistência natural foi influenciada pelos fatores e os painéis foram inclusos na categoria \"resistência moderada\". Os resultados do Experimento II mostraram que as partículas tratadas em água quente resultaram em aumento significativo dos valores de IE2h, IE24h e TNRE. O APS, APT e LI apresentaram melhorias significativas para os painéis manufaturados com partículas tratadas em água quente. Os fatores avaliados influenciaram a massa específica aparente da camada externa dos painéis. Houve interação significativa entre os fatores para o ângulo inicial obtido com água. O fungo G. trabeum causou maiores perdas de massa nos painéis constituídos com partículas tratadas em água quente e o T. versicolor evidenciou maior índice de ataque em chapas confeccionadas com partículas controle. No Experimento III o aumento da razão de compactação apresentou tendência significativa de aumento de valores da AA24h, IE2h, IE24h e TNRE, além do MoR. Tal variável reduziu a AA2h, APT e LI, proporcionou picos mais acentuados de massa específica nas faces dos painéis, reduziu significativamente a molhabilidade e aumentou a perda de massa dos painéis submetidos aos fungos P. placenta e G. trabeum. No Experimento IV o tratamento térmico promoveu melhorias significativas para AA2h, AA24h, IE2h e IE24h, porém reduziu o MoR, MoE, APS, APT e LI, que foram melhoradas com o aumento no teor de adesivo, além do perfil de densidade. Não houve influência significativa na molhabilidade, comparando os painéis com mesmo teor de adesivo e nem considerando diferentes teores de adesivo. De forma geral, os painéis apresentaram melhorias significativas na resistência biológica com a termorretificação e aumento no teor de adesivo. Bagaço de cana-de-açúcar e bambu representam boas alternativas de matérias-primas para confecção de chapas aglomeradas. Os painéis podem ser utilizados para forros, isolamento térmico e acústico, revestimentos, painéis decorativos, componentes para construção civil, substrato para piso, embalagens, pequenos objetos entre outras aplicações. / The aiming of this study was to evaluate the quality of medium density particleboard (MDP) manufactured with particles of sugarcane bagasse and bamboo with nominal density of 0.65 g.cm-3 and urea-formaldehyde adhesive. The experimental design was composed of 16 treatments divided in four experiments. The physical properties (apparent density, water absorption, thickness swelling and the nonrecoverable tax, mechanical (static bending - modulus of elasticity and modulus of rupture, screw withdrawal strength and internal bonding) were evaluated, as well as the density profile, wettability and natural resistance. The objectives were: I - To evaluate panels of sugarcane bagasse particles with two granulometries (0.50 mm and 0.85 mm) treated and not treated in hot water; II - To evaluate the panels using the same variables of the previous experiment, however using bamboo particles; III - Evaluate the panels origin from the mixture of both materials in proportions of 100%, 75%, 50%, 25% and 0%; IV - Evaluate the panels constituted with heat treatment particles of bamboo and bagasse and glued with three adhesive contents (10, 12 and 14%). The results of the Experiment I showed that physical (IE2h, IE24h, AA24h and TNRE) and mechanical properties (MoR, MoE, APS, APT and LI) and wettability were not influenced by the factors (grain size and particle condition). The factors influenced the apparent specific bulk density profile of the outer layer. Natural resistance was influenced by the factors and the panels were included in the \"moderate resistance\" category. The results of Experiment II showed that the particles treated in hot water resulted in a significant increase in the values of IE2h, IE24h and TNRE. APS, APT and LI showed significant improvements for panels manufactured with hot water treated particles. The evaluated factors influenced the apparent specific mass of the outer layer of the panels. There was a significant interaction between the factors for the initial angle obtained with water. The G. trabeum fungus caused greater mass losses in the panels constituted with particles treated in hot water and T. versicolor evidenced a higher attack rate in plates made with control particles. In Experiment III the increase in compaction ratio showed a significant tendency to increase values of AA24h, IE2h, IE24h and TNRE, in addition to MoR. This variable reduced AA2h, APT and LI, provided more pronounced peaks of specific mass in the faces of the panels, significantly reduced wettability and increased the mass loss of the panels submitted to P. placenta and G. trabeum fungi. In Experiment IV the heat treatment promoted significant improvements for AA2h, AA24h, IE2h and IE24h, but reduced MoR, MoE, APS, APT and LI, which were improved with the increase of the adhesive content, as well as the density profile. There was no significant influence on wettability, comparing the panels with the same adhesive content and different adhesive contents. In general, the panels showed significant improvements in the biological resistance with thermortification and increase in the adhesive content. Sugarcane bagasse and bamboo represent good alternatives of raw materials for confection of agglomerated sheets. The panels can be used for linings, thermal and acoustic insulation, coatings, decorative panels, components for civil construction, substrate for flooring, packaging small objects among other applications.

Les matériaux composites à matrice céramique CMC, sont généralement formés d’au moins deux matériaux ayant une forte capacité d’adhésion. Ces matériaux sont principalement composés de renforts fibreux assurant la tenue mécanique de la structure et d’une matrice qui permet sa cohésion. Utilisées principalement dans le domaine de l’aéronautique, elles sont reconnues pour leur bonne tenue mécanique, leur réfractarité élevée tout en conservant une densité faible. Par contre, l’inconvénient majeur associé à ces matériaux est l’apparition de fissures qui sont dues soit au procédé de fabrication soit aux sollicitations mécaniques externes.Dans ce travail, une attention toute particulière est consacrée aux composites à matrice auto-cicatrisante dont la principale propriété est l'aptitude à "réparer" les effets de la fissure par formation d'un verre visqueux.Ces verres visqueux se forment au sein de la fissure grâce à l’oxydation des éléments qui constituent la matrice. Selon la température, différents verres peuvent être formés.Leur fonction est de reboucher les fissures de taille micrométrique de façon à ralentir la diffusion de l'oxygène en direction des fibres et éviter leur rupture par oxydation.Cependant, pour des systèmes en rotation rapide tels que les turbines basse pression des moteurs d’avion (pièce étudiée actuellement), on peut s'interroger quant à la mobilisation du verre visqueux cicatrisant dans un système complexe géométriquement et inhomogène du point de vue de la nature des surfaces. Pour approcher le comportement du verre cicatrisant dans un système modèle mais néanmoins réaliste, une approche de modélisation numérique a été entreprise. L'outil numérique utilisé pour cette étude est le code de calcul Thétis développé à l’I2M. Celui-ci est adapté à ce type de simulation puisqu'il permet la modélisation d'écoulements diphasiques incluant des phénomènes physiques complexes tels que le mouillage. Ainsi, l'objectif de ce travail est-il de déterminer les limites d'utilisation de ce type de matériau en fonction des conditions auxquels il est soumis en évaluant la mobilité du verre cicatrisant dans la fissure. / The Ceramic Matrix Composites (CMCs) are generally formed of at least two materials having strong adhesion ability. These materials are mainly composed of fibrous reinforcement which ensures the mechanical resistance of the structure and a matrix which allows its cohesion.Used mainly in aerospace, the CMCs are highly valued for their good mechanical strength, their good refractory properties associated with a low density.However, the major drawback of these materials is cracks formation due to manufacturing process or to external mechanical stresses.In this study, we focus on composite materials having self-healing properties. These materials have the ability to produce healing viscous glasses in presence of oxygen.These viscous glasses are formed in the crack under the influence of oxidation of matrix compounds. Depending on the temperature level, glasses of different natures are formed.Their main role is to reseal the micrometric cracks, to limit oxygen access to the fibers in order to prevent their rupture by oxidation.However, for fast rotating systems such as the low pressure turbine of aircraft engines, we may question about mobilization of such a viscous glass in a system characterized by a complex geometry and chemically inhomogeneous surfaces.Therefore, a numerical approach was undertaken, using "Thetis" software. Developed at I2M, this software allows us modelling two-phase flow in model simplified geometry (reflecting however reality) including complex phenomena such as wetting. Numerical results yield to the determination of operating limitations of CMCs in terms of healing efficiency as a function of external mechanical stresses (rotation) and crack geometry.

Existe atualmente uma crescente produção de leite de búfala no Brasil e no mundo, sendo que 13% do leite mundial é produzido por esta espécie, perdendo somente para a produção do leite bovino. Esse crescimento deve-se às características peculiares do leite desta espécie em comparação ao bovino, incluindo teores mais elevados de vitamina C, minerais (como cálcio e fósforo), gordura e proteína. Uma alternativa para dar maior rentabilidade econômica ao leite consiste na transformação do produto para a forma de pó de fácil reconstituição (instantâneo) através de um processo de secagem. Como a reconstituição de um alimento em pó depende significativamente das suas características de molhabilidade, é comum a utilização de processos como aglomeração e lecitinação para melhorar a molhabilidade do leite em pó. Neste contexto, o objetivo deste estudo consiste em investigar a influência da adição de lecitina, antes da secagem por atomização, na molhabilidade do leite de búfala em pó. Com esta finalidade, o leite de búfala in natura foi semidesnatado, pasteurizado, concentrado a 40% (percentual mássico) de sólidos totais e seco por pulverização. Nos produtos preparados com lecitina, este aditivo foi utilizado em proporções de 0,3, 0,5 e 1,0 g de lecitina/100 g de sólidos totais no leite concentrado, previamente ao processo de secagem por atomização. Nestas condições, o efeito da concentração de lecitina na molhabilidade do leite em pó produzido foi avaliado através da técnica de Washburn e do teste de molhamento estático. Ainda, o material seco foi avaliado quanto ao teor de umidade, distribuição de tamanho de partículas e, para amostras específicas, quanto à área superficial, atividade de água, cor e morfologia das partículas (via microscopia eletrônica de varredura). Foi observado que a adição de lecitina diminuiu o tempo de molhamento (valores compreendidos entre 63,9 e 188,4 s) quando comparado ao leite in natura (300,9 s). O ângulo de contato das amostras de leite em pó obtidas em níveis superiores a 0,3% de lecitina adicionada diminuiu significativamente, para valores compreendidos entre 82,73 ± 2,76° e 81,21 ± 2,23°, com relação ao valor obtido sem adição do aditivo (89,01 ± 0,48°). Entretanto, a presença de lecitina não apresentou considerável influência na umidade, atividade de água, cor, morfologia, área superficial e na distribuição de tamanho das partículas obtidas. / There is nowadays a growing production of buffalo milk in Brazil and in the world. It already represents 13% of total world milk production, being second only to the production of bovine milk. This growth is due to the peculiar characteristics of this kind of milk compared to cow milk, such as higher content of vitamin C, minerals (such as calcium and phosphorous), fat and protein. An alternative to provide greater economic return from milk consists in converting the product to powder for easy reconstitution (i.e. instant food) through a drying process. As the reconstitution of a powdered food depends strongly on its characteristics of wettability, the utilization of alternatives such as agglomeration and addition of lecithin are commonly used to improve the wettability of the final product. In this context, the aim of this study is to investigate the influence of the addition of lecithin, previously to the spray drying on the wettability of buffalo milk powder. For such purpose, the fresh buffalo milk was partially-skimmed, pasteurized, concentrated to 40% (mass percent) of total solids and spray-dried. Four milk powders were produced, one without addition of lecithin and three with different contents of lecithin (0.3, 0.5 and 1.0 g of lecithin/100 g of total solids). The effect of the concentration of lecithin on the wettability of the powder produced was measured by the Washburn technique and static wetting test. Further, the dried material was analyzed for moisture content, particle size distribution, and for specific samples, for surface area, water activity, color and particle morphology (scanning electron microscopy). It was observed that the addition of lecithin decreased the wetting time (values comprised between 63.9 and 188.4 s) when compared to lecithin-free milk (300.9 s). The contact angle of the milk powder samples obtained with levels greater than 0.3% of added lecithin significantly decreased to values between 82.73 ± 2.76° and 81.21 ± 2.23°, with respect to the value obtained without addition of the additive (89.1°). However, the presence of lecithin showed no significant influence on the moisture content, water activity, color, morphology, surface area and particle size distribution of the produced powders.

Orientador: Osvair Vidal Trevisan / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-29T00:01:03Z (GMT). No. of bitstreams: 1 RuidiazMunoz_Eddy_D.pdf: 4515503 bytes, checksum: 70497e20d04fea10c0814c3960b218d9 (MD5) Previous issue date: 2015 / Resumo: Em caracterização de reservatórios, é importante estudar e entender propriedades chaves na produção de petróleo. Em reservatórios carbonáticos, uma destas propriedades é a molhabilidade. Diretamente relacionada à interação rocha/fluido no reservatório, pode variar entre molhabilidade intermediária e a preferencial ao óleo. O objetivo principal deste trabalho foi o de estudar o mecanismo de alteração da molhabilidade em rochas de coquinas e dolomita de afloramentos. Foram realizados experimentos usando água com concentração de 35kppm e 200kppm de cloreto de sódio, água do mar modificada na composição iônica e água enriquecida com CO2. Inicialmente foram caracterizadas as rochas na sua estrutura e composição mineral seguido de um teste de forças capilares e molhabilidade inicial. Em seguida, foi investigada a adsorção/dissolução de ións de sulfato. Com o propósito de obter rochas com molhabilidade ao óleo, foi realizado um estudo de envelhecimento baseado no tempo de contato utilizando óleo morto e uma mistura constituída por óleo mineral e ácido naftênico (2%) sobre uma condição de saturação de 100%. A partir destes resultados foram preparadas rochas com saturação de água irredutível para medir a molhabilidade através de embebição espontânea e do índice de Amott_Harvey. As águas utilizadas foram salmouras em diferentes concentrações salinas, salmoura carbonatadas e água do mar modificada. Para encerrar o estudo, foram realizadas trocas de concentração salina e iônica, para observar os efeitos na recuperação e associá-los com a alteração da molhabilidade. Os resultados obtidos no estudo do envelhecimento, as coquinas não apresentaram variações na recuperação durante os tempos utilizados. Já para as rochas de dolomita, conforme se aumentou o tempo de envelhecimento, a recuperação diminuiu consideravelmente, fenômeno diretamente associado à adsorção de componentes polares durante o envelhecimento. Além disso, as rochas de dolomita responderam positivamente às trocas de concentração salina. No caso do uso de água do mar modificada, os resultados mostram que para as rochas de dolomita apresentaram-se dois cenários no fenômeno de alteração da molhabilidade; o primeiro relacionado com a presença de sulfato na água do mar e/ou a remoção do cloreto de sódio, e o segundo com a injeção de água de baixa salinidade. Para as rochas de coquina o fator relevante para obter volumes adicionais por efeitos da alteração da molhabilidade foi o acréscimo de concentração de sulfato, com a remoção do cloreto de sódio da água utilizada ou o uso de água do mar com altas concentrações de sulfato. Finalmente o estudo do efeito do CO2 na alteração da molhabilidade mostrou que, tanto pela embebição espontânea quanto pelo índice Amott_Harvey, a molhabilidade não é alterada significativamente com o uso de água carbonatada / Abstract: In reservoir characterization, it is important to study and understand properties that are key in oil production. One of these properties in carbonate reservoirs is rock wettability. Directly related to the reservoir rock/fluid interaction, rock wettability can vary from intermediate to preferably oil-wetting. The main objective of this work was to study the mechanism of wettability alteration in limestone and dolomite outcrop rocks. Experiments were carried out using sodium chloride brines at 35kppm and 200kppm, seawater brines modified in its ionic composition and sodium chloride brines at 35kppm and 200kppm enriched with CO2. Initially, the rocks samples were characterized in their mineralogy and structure and initial wetting and capillary forces. In the sequence tests were performed with the samples to investigate adsorption/dissolution of sulfate ions. In order to attain oil-wetting conditions, an aging study using dead oil or a mixture composed by synthetic mineral oil and naphthenic acid (2%) was undertaken, focusing contact time. After these results, rocks were prepared at irreducible water saturation for measuring the wettability by spontaneous imbibition and Amott_Harvey wettability index. Injection water was: brines of different salinities, modified seawater and brines enriched with CO2. To close the study, salinity and ionic concentration were switched, in order to check for additional recoveries and associate them with wettability alteration. The results obtained from the aging, study show that limestone had no variations in oil recovery for the aging time evaluated. In the case of dolomites, there was increase on oil recovery as the aging time increased. The occurrence is attributed to the adsorption of polar components during the aging. In addition, additional recoveries were obtained for dolomites with the switch of brine concentration. For the modified seawater, the results showed that wettability alteration in dolomite presented two scenarios; the first is related to the presence of sulphate ions in seawater or with the removal of sodium chloride, and the second one, the injection of low salinity water. For the limestone, the relevant factor for wettability alteration was the increase of sulfate ions associated with removal of sodium chloride from seawater or the use of seawater spiked with high concentrations of sulfate. Finally, there was no significant change on rock wettability when carbonated water was used. Both spontaneous imbibition and Amott_Harvey indices show no relevant effect of CO2 regarding wettability alteration / Doutorado / Reservatórios e Gestão / Doutor em Ciências e Engenharia de Petróleo

O objetivo desse estudo foi avaliar o efeito da quitosana nas concentrações de 2,5% e 5,0% na molhabilidade da dentina erodida. 104 espécimes de dentina bovina (7,0x7,0x2,5) foram planificados e polidos, e para o desafio erosivo os espécimes foram imersos em 20mL de ácido cítrico (pH=3.2) sob agitação durante 2h. Os espécimes foram divididos aleatoriamente de acordo com o substrato dentinário: hígido e erodido e subdivididos em 4 grupos (n=10): sem reumidificação (controle), ácido acético a 1%, quitosana a 2,5% e quitosana a 5,0%. Em seguida, uma gota do sistema adesivo Single Bond 2 (3M) foi depositada sobre a superfície de cada espécime. Os ângulos de contato entre a superfície de dentina e o adesivo foram mensurados por meio de um goniômetro. Os outros 24 espécimes foram submetidos à análise da superfície por meio MEV. Os testes estatísticos utilizados foram o teste de normalidade (Kolmogorov-Smirnov) e análise de variância (ANOVA) (p>0,05). Não foram encontradas diferenças entre os ângulos de contato produzidos na dentina erodida reumidificada com quitosana nas concentrações de 2,5% e 5,0%. A solução de quitosana, independente de sua concentração, não influenciou na molhabilidade da dentina erodida. Através de análise em MEV, verificou-se que houve deposição de partículas de quitosana sobre a superfície e no interior dos túbulos dentinários. / The aim of this study to assess the effect of chitosan, in concentrations of 2.5% and 5.0%, on the eroded dentin wettability, followed by analysis of surface morphology by SEM. 104 bovine dentin slabs were ground, polished and then immersed in 20mL of citric acid (pH = 3.2) under continuous stirring for 2h. Specimens were randomly divided according to the dentin substrate: sound and eroded, and then, subdivided into 4 groups (n=10): without rewetting (control), 1% acetic acid, 2.5% chitosan and 5.0% chitosan. Then, a drop of the adhesive system Single Bond 2 (3M) was deposited onto surface of each specimen. The contact angle between dentin surface and the adhesive system was measured by using a goniometer. The other 24 specimens were subjected to analysis under SEM. Statistical analysis was performed using the normality test (Kolmogorov-Smirnov) and Analysis of Variance (ANOVA) (p> 0.05). No differences were found between the angles produced on the eroded dentin re-rewetting with chitosan in the concentrations of 2.5% and 5%. The chitosan solution, regardless of the concentration used, did not influence of the eroded dentin wettability. Through SEM analysis, it was found particles of chitosan deposited on the surface and within the dentinal tubules.

<div>Plasma treatment of polymers has been a rapidly growing area of research due to its broad applications, homogenous and repeatable surface properties, low cost, and environmental friendliness when compared to alternative techniques. Only recently have significant developments been made in the application of atmospheric pressure plasma in polymer surface treatment. The use of atmospheric pressure plasma enables further reductions in cost and mechanical complexity. Of particular interest in this work is the application of atmospheric pressure plasma for the isolated modification of the inner surfaces of small diameter polymer tubing to improve the wetting and adhesion characteristics compared to untreated polymer.</div><div>This work focuses on the development, characterization, and implementation of an atmospheric pressure dielectric barrier discharge (DBD) plasma apparatus for the treatment of the inner surface of polymer tubes. The iterative process of the development of this system is detailed, with two finalized designs established and defined. These two designs are then applied to low density polyethylene (LDPE) tubing of 0.38 mm inner diameter (ID), and characteristics for surface morphology and wettability are analyzed.</div><div>Investigation of the relationship between plasma power and treatment time with morphology characteristics of protrusion density and size and surface roughness parameter, R_a is presented. Treatment times of 5, 10, 15, 30 and 45 minutes are performed on tubing samples at a power level of 35 mW. From 5 to 15 minutes, protusion density increases rapidly, from n_p=4*10^4- 10^7 protrusions/(mm^2 ), and small variation in protrusion size, with 0.1< A_p<0.2 μm^2. At treatment times of 30 and 45 minutes, coalescence of protrusions was observed, resulting in a decrease in protrusion density, down to n≈4*10^4 protrusions/(mm^2 ), and substantial increases in mean protrusion size, up to A_P=5-9 μm^2. Plasma powers of 9, 12, 16, 25, 35, and 45 mW were also investigated, at a treatment time of 15 minutes. As power level was increased, protrusion density was observed to increase, with an inverse relationship with mean protrusion size. Protrusion density was observed to increase from n_p=2*10^5-10^7 protrusions/(mm^2 ), with diminishing increases in density observed between power levels of 35 and 45 mW. Protrusion mean size was observed to decrease from A_p= .25-0.025 μm^2, with similar diminishing reductions observed at 35 and 45 mW. Surface roughness, R_a, was observed to vary from .01-0.3 μm, or ISO roughness grades N1 to N5, in the treated samples.</div><div>Wettability characteristics were measured and characterized relative to plasma power and linear feed rate. Wettability was measured by measurement of contact angles of the meniscus formed from water introduced into the tubing volume by capillary action. On all samples treated, a duality of mechanisms for surface wetting were observed. After initial treatment, samples were observed to have a lower contact angle, indicating higher wettability, but after 12 hours samples were observed to have reduced wetting characteristics, indicating a transient mechanism for surface wetting in addition to permanent effects induced my surface morphology. Samples were treated at plasma powers of 7, 10, 15, 20, and 40 mW. At all power levels, initial contact angle was generally consistent, with 20^o< θ_0<30^o. Permanent wetting features measured on these samples indicated almost complete reversing of wettability at 7 and 10 mW, with θ_SS measured at ~75^o, comparable to the average measurement of an untreated sample of ~80^o. Conversely, at higher powers of 15, 20 and 40 mW, significant retention of wettability was observed, with 45^o<θ_SS<55^o for those samples.</div><div><br></div>

This work deals generally with surface diagnostic and optical properties of thin layers which are created by plasma polymerization of hexamethyldisiloxane monomer. The influence of oxygen adittion on thin layers properties was studied, too. This polymer layers are commercially made to protect reflective layers in the headlights. Thin layers were made in deposition chamber AluMet 1800V at Zlin Precision Company. Teoretical part of this work deals with methods which are used for deposition of thin layers, mainly physical (PVD) and chemical (PECVD, CVD) depositions. The conditions which influenced plasma polymerization itself are discussed as well as, monomers which are used for plasma polymerization and stability of thin polymer layers. Also there are mentioned the most frequent plasma processes diagnostic methods applicable during the deposition (optical emission spectroscopy) and methods for thin layers diagnostic (wettability, UV-VIS and infrared spectroscopy). Spectrometer Jobin Yvon Triax 320 was used for emission spectra acquisition during the plasma deposition. There were analyzed only two spectra created at same conditions as power at 3 kW and monomer flow rate at 100 sccm; the first one was in pure monomer, the second was obtained with oxygen addition of 150 sccm into the monomer flow. There was not found any essential differences between these spectra in the range 300 nm to 800 nm. Besides the thin layers analyzes after their formation, the samples were exposed to common aging conditions with respect to their use. One third of the prepared samples was exposed by ultraviolet radiation for 48 hours (exposure power of 0.68 W.m-2 at 340 nm) and the other part of samples was inserted for four days into NaCl solution of 50 g.l-1. The surface properties of layers were studied by their contact angle with three liquids (water, diiodmethane, and glycerol) that allowed their surface energy calculation. Results of this measuring are as following: Oxygen addition decreased contact angle of water after exposure of UV radiation. If the highest flow rate of monomer was used and oxygen was added, NaCl degradation did not have any significant influence on contact angle to water. Optical properties of prepared thin films were characterized by UV-VIS spectroscopy. Optical properties were measured only for samples after deposition and samples that were exposed by ultraviolet radiation. Results showed that oxygen addition into the reacting mixture increased the light absorption in UV-VIS (300-800 nm). The absorption was significantly increased after exposure of ultraviolet radiation. With respect to the application of these thin layers is necessary to say that this influence is undesirable. On the other hand, absorption of thin layers deposited at 2 kW, without oxygen addition and flow rate of monomer at 125 sccm a 150 sccm was decreased. Results of this work can be useful for investigation and study of deposited thin layers. The most useful can be with another work which deals with plasma diagnostics during the deposition even more closely. Then it will be possible to adjust and predict properties of deposited layers.

This work consider with monitoring components of komplex permittivity at frequency section of electro-insulation material in process of wetting by dielectric relaxation spectroscopy.